1) Field of the Invention
The present invention relates to a cartridge transferring robot for use in a library apparatus which stores a large number of cartridges such as magnetic tape cartridges and optical disk cartridges, with the cartridge transferring robot taking the charge of the conveyance of the cartridges among a storage unit (or rack), a cartridge entry/exit station and a drive unit within the library apparatus.
2) Description of the Related Art
In general, a library apparatus functions as a large-capacity external storage unit, and a storage unit in its locker stores several thousands of cartridges each accommodating, for example, a magnetic tape as a storage medium, and access such as write/read of recording/recorded data is automatically done toward the storage medium within each of the cartridges.
Furthermore, in addition to the aforesaid storage unit for storing the cartridges, the library apparatus is equipped with a station [for example, a CAS (Cartridge Access Station), a DEE (Direct Entry/Exit), and an FES (Forced Exit Station)] for carrying out the entry of the cartridges from the external into the apparatus or vice versa, a plurality of magnetic tape drive units (which will be referred hereinafter to as MTUs) for conducting access such as write/read of recording/recorded data toward a storage medium (magnetic tape) within a cartridge, and a cartridge transferring robot [automatic transferring robot; which will be referred hereinafter to as an accessor (ACC)] for performing the conveyance among the storage unit, the cartridge entry/exit station and the MTU.
In the case of such a library apparatus, on receiving an access demand to one cartridge from a host unit or the like, the accessor moves to the storage unit to search the directing cartridge and then transfers that cartridge up to the MTU in a state of gripping or holding it through the use of a hand mechanism, thereby putting it in the MTU. Whereupon, the MTU processes the storage medium (magnetic tape) within the cartridge. The cartridge discharged from the MTU after the completion of the processing is regripped by the hand mechanism of the accessor and transferred up to the storage unit by that accessor to be stored in a given location.
The accessor to be employed for the foregoing library apparatus is composed of a picker section including a hand mechanism for inserting and pulling out a cartridge in a state of gripping it, a moving mechanism for shifting this picker section to a given position, and a tilt mechanism (see FIG. 23) for adjusting an angle to be made with respect to a horizontal direction at the insertion and extraction (pulling-out) of the cartridge.
Thus, while transferring the cartridge, that cartridge is conveyed by the moving mechanism to the given position in a state of being gripped by the hand mechanism and taken into the interior of the picker section, and subsequently put in a unit (a cell of the storage unit or the MTU) at the given position. At this time, because of taking different insertion/extraction angles of the cartridges for the respective units, there is a need to change the cartridge insertion/extraction angle taken by the hand mechanism.
As the cartridge inserting/extracting direction (angle) of the hand mechanism 112, for example there are taken a horizontal direction (0.degree.) and a direction looking (inclined) downward by a given angle with respect to the horizontal direction. In the case of the MTU, in general the cartridges are inserted and pulled out in/from the horizontal direction (0.degree.). On the other hand, in the case of the storage unit or the like, the cartridges are set in a condition looking downward (for example, 12.degree.) relative to the horizontal direction to prevent them from dropping from the cells of the storage unit due to the vibrations caused by earthquakes and others, and therefore, the insertion and extraction of the cartridges are made at that angle.
For these reasons, the accessor is provided with a tilt mechanism 100, for example, as shown in FIG. 23. This tilt mechanism 100 comprises a tilt base (not shown) for supporting a picker section 110 so that the picker section 110 is swingable about or around a supporting shaft (spindle) 111 protrusively stood at a side surface of a substantially central portion of the picker section 110 in the forward and backward directions (in the left- and right-hand directions in FIG. 23), and a swinging drive mechanism 120 for making the picker section 110 rock around the supporting shaft 111 with respect to this tilt base.
The picker section 110 incorporates a hand mechanism 112 which is movable in the forward and backward directions and made to insert and draw a cartridge while gripping it, and as mentioned before, the cartridge held by the hand mechanism 112 is introduced into the picker section 110 at the cartridge conveyance. In FIG. 23, a mechanism for moving the hand mechanism 112 in the forward and backward directions is omitted from the illustration.
Furthermore, the swinging drive mechanism 120 is made up of a cam follower 121 protrusively set upright on its side surface on the front side of the picker section 110 which is in opposed relation to the cartridge inserted and extracted unit (storage unit, cartridge entry/exit station, MTU, and others), a plate cam 122 fitted to be movable in the cartridge inserting/extracting (drawing) direction with respect to the tilt base for guiding the cam follower 121 in the vertical directions in accordance with its movements in the forward and backward directions, and a drive mechanism (not shown) for moving the plate cam 122 in the cartridge inserting/extracting direction with respect to the tilt base.
The plate cam 122 has an elongated guide hole 122a made to extend in the forward and backward directions, and a pair of guide rollers 123, 123 installed on the tilt base side are fitted in this elongated guide hole 122a. Further, a pair of guide rollers 124, 124 set on the tilt base side in the forward and backward directions are placed into contact with a horizontal lower edge portion 122c of the plate cam 122 from the below. Whereupon, the plate cam 122 is set up on the tilt base to be movable in the cartridge inserting/extracting direction while being guided by the guide rollers 123, 124.
In addition, the plate cam 122 incorporates a rack 122d which gears with a pinion (not shown) fitted over a drive shaft of a tilt motor (not shown). Accordingly, when the pinion is rotationally driven by the tilt motor, this rotational movement is converted into a linear movement of the plate cam 122 through the rack 122d gearing with this pinion, so that the plate cam 122 is driven in the cartridge inserting/extracting direction. That is, the tilt motor, the pinion and the rack 122d constitute the aforesaid drive mechanism.
Moreover, the plate cam 122 has an elongated rocking drive hole 122b engaging with the cam follower 121. This elongated rocking drive hole 122b includes two horizontal portions 122b-1, 122b-3 different in height from each other and an inclined portion 122b-2 making the connection between these horizontal portions 122b-1, 122b-3.
The front side horizontal portion 122b-1 serves as a portion for maintaining the picker section 110 in the horizontal condition. As shown in FIG. 23, in a state where the cam follower 121 is located at the horizontal portion 122b-1 of the elongated hole 122b, the picker section 110 takes the horizontal condition, and the cartridge inserting/extracting direction depending upon the hand mechanism 112 are maintained to assume the horizontal directions.
On the other hand, the rear side horizontal portion 122b-3 is at position lower than the front side horizontal portion 122b-1, and serves as a portion for maintaining the picker section 110 in the tilt condition in which the front surface of the picker section 110 is directed downwardly by a given angle (for example, 12.degree.) from the horizontal direction. If the plate cam 122 is shifted forwardly (in the left-hand direction in FIG. 23) from the state of FIG. 23 and the cam follower 121 is guided and shifted from the horizontal portion 122b-1 through the inclined portion 122b-2 to the horizontal portion 122b-3, the picker section 110 comes into the tilt condition, and the cartridge inserting/extracting direction of the hand mechanism 112 is maintained to be inclined downwardly by a given angle (for example, 12.degree.) from the horizontal direction.
In the prior library apparatus, each of the MTUs is equipped with a dedicated cartridge giving and receiving mechanism, and the accessor takes the charge of only handing over the cartridge to the cartridge giving and receiving mechanism, whereas the cartridge giving and receiving mechanism accomplishes the actual insertion of the cartridge into the MTU. In addition, the cartridge taken out from the MTU is handed over through the cartridge giving and receiving mechanism to the accessor. Accordingly, in the prior art, the positional accuracy of the tip portion of the hand mechanism needs not be relatively high.
However, recently, for the purpose of the size reduction and low manufacturing cost of the library apparatus, it is desirable that the cartridge giving and receiving mechanism is omitted so that the accessor directly conducts the insertion and extraction of the cartridge into/from the MTU. This requires the considerable improvement of the positional accuracy of the tip portion of the hand mechanism being in the advanced condition.
In the prior tilt mechanism 100 shown in FIG. 23, the supporting point (i.e., the position of the supporting shaft 111) on the tilt action stands at the center of picker section 110 in the forward and backward directions, while the effort point (i.e., the position of the cam follower 121) is on the front side of the picker section 110. Thus, in the prior tilt mechanism 100, the distance L.sub.1 from the supporting point to the effort point is set to be short, thereby changing the attitude of the picker section 110, i.e., the cartridge inserting/extracting direction of the hand mechanism 112, without moving the picker section 110 in a large way. Accordingly, the moving quantity of the picker section 110 in the height directions is reduced to cope with the restriction in the mounting space around the picker section 110. This signifies that no consideration is paid to the positional accuracy of the tip portion of the hand mechanism 112 being in the advanced condition.
That is, in the case of the prior tilt mechanism 100 shown in FIG. 23, the distance L.sub.2 from the supporting point to the tip position of the hand mechanism 112 is set to be considerably longer than the distance L.sub.1 from the supporting point to the effort point, and therefore, the dimensional error dy at the effort point results in being enlarged and amplified to L.sub.2 /L.sub.1 (&gt;1) times at the tip position of the hand mechanism 112. For this reason, the positional accuracy at the tip portion of the hand mechanism deteriorates, so that difficulty is encountered to ensure the positional accuracy whereby the accessor can directly accomplish the insertion and extraction of the cartridge into/from the MTU.